1. Field of the Invention
The present invention relates to a cordless telephone.
2. Description of the Prior Art
In a low power cordless telephone available on the Japanese market, 87 communication channels and two control channels are available, in which each channel is a duplex channel.
In the standby mode of such conventional cordless telephone, a handset unit (remote station) intermittently receives and monitors a control channel having a predetermined frequency, whereupon when telephone communication is desired, the handset unit utilizes a communication channel specified by the control channel.
In Japan, there also exists a low power cordless telephone which does not use a control channel. Further, a cordless telephone used in the United States of America has 10 duplex channels, that is, channels 1-10, but does not have a control channel.
In the cordless telephones which do not have control channels as mentioned above and, as described, for example, in U.S. Pat. No. 4,768,219, the base unit (master station), which receives power from a commercially available power source, sequentially receives and monitors the first to tenth channels repeatedly when in a standby mode while awaiting a connection request from the handset unit.
The handset unit, while in the standby mode, also receives and monitors the first to tenth channels so as to determine if a connection request was sent from the base unit. As is to be appreciated, since the handset unit utilizes a battery as its power source and the handset unit continuously repeats the scanning of the 10 channels in the standby mode, the power consumption is considerably large and, as a result, the battery must be frequently changed. If, however, the handset unit utilizes a rechargeable battery, such rechargeable battery must still be frequently recharged, which may be very inconvenient for the user.